Research Review on Childhood Leukemia and Residential Proximity to Industrial and Urban Sites

Abstract

The current trend is residential proximity of industrial and urban sites being a risk factor in causing leukemia. Although there are many risk factors that cause leukemia, the role of industrial and urban pollution needs to be assessed. People need to be aware of every possible risk factor in causing cancer. The study done is a population-based control study. The goal of this study was to analyze the effects of exposure to industrial and urban areas on childhood leukemia.

Introduction

Leukemia is a rare form of cancer, which hinders the body’s ability to fight infection. Leukemia symptoms include fatigue, weight loss, frequent infections, bleeding and bruising. According to Peris-Bonet (2010), “Childhood cancer is the leading cause of disease-related death in childhood affecting both sexes worldwide and, therefore, is an important concern for public health, medical care, and society.” “The main group is leukemia…” (Peris-Bonet et al., 2010). Leukemia is the most common around children under the age of 15. The annual incidence rate of leukemia is 43 cases per million. Learning more about the risk factors contributing to the cause of cancer will help reduce the amount of children who will be diagnosed with leukemia. For example, the parent may respond a different way if he or she knows a way that they can prevent the cancer. However, if the parent does not know all the possible risk factors then he or she will respond differently when the child has been diagnosed. This study will further advance the knowledge and potential risk factors that may cause childhood leukemia. The knowledge of knowing what causes leukemia can lead to a lesser diagnoses rate. This research article will discuss which industrial plants and urban sites will increase the risk of childhood leukemia. This study will also further advance the research by bringing awareness to the metal industry, glass and mineral fibers, pharmaceuticals products, hazardous waste, and surface treatments using organic solvents showing an increased risk. Not only does those above show an increased risk in cancer, but so does living in the proximity of installations releasing carcinogens, non-HPCs, plasticizers, pesticides, solvents, POPs, PACs, metals, and VOCs.

Materials & Methods

Data for this study was collected from the Spanish Registry of Childhood Tumors. This study was designed in Spain as a population-based control study. The controls for this design were selected by random sampling. The children ranged from the ages 0 months to 14 years of age. The population contained 638 cases and 13, 188 controls. Each of the controls were matched by birth year, sex, and by their residence. The distance between the residents, the industrial site, and urban areas was all computed in the industrial database provided by the Spanish Ministry for Agriculture Food and Environment. There are a total of 1,068 industries and 157 urban sites. The installations in this study were classified into 25 different categories.

Results

In Table 2, they distributed the cases by sex, birth year, region, and type of leukemia. Males had the highest proportion of cases and controls (57.8 % and 56 %) and females had the lowest proportion of cases and controls (42.2% and 44 %). There are four different regions that were included in this study; Catalonia, Basque Country, Aragon, and Navarre. Catalonia region has the highest proportion of cases and controls (65.5 % and 67.2%), followed by Basque Country with (18.7% and 16.5%), then Aragon with (9.4% and 9.8%), lastly Navarre with (6.4% and 6.5%). This table also shows us that lymphoid leukemia is the main type of childhood leukemia with (81.5%). In Table 3, children living between 1.5 and 2.5 km for both industrial and urban sites showed an increased risk of childhood leukemia. For industrial sites at the 2.5 km distance (adjusted- OR = 1.31; 95%Cl = 1.03-1.67). For urban sites there is also an excess risk (adjusted –OR = 1.36; 95%Cl =1.02-1.80). In Table 4, glass and mineral fibers (adjusted- OR =2.42), surface treatment using organic solvents (adjusted-OR = 1.87), galvanization (adjusted- OR = 1.86), production and processing metals (adjusted- OR = 1.69), surface treatment of metals and plastics (adjusted- OR =1.69), hazardous waste (adjusted- OR =1.55), and pharmaceutical products (adjusted- OR=1.53) all show an increased risk of childhood leukemia in their environs. In Table 5, children living close to industrial facilities releasing carcinogens substances and toxic substances showed the highest amount of an increased risk of leukemia. The adjusted ORs =1.35 for releasing Group 1 carcinogens and 1.48 for Group 2A and 1.54 for Group 2B. The groups of the toxic substances also show an increased risk near HPCs (adjusted-OR=1.71), plasticizers (adjusted-OR=1.67), pesticides and solvents (adjusted-ORs=1.61 in both cases), POPs (adjusted-OR=1.58), PACs (adjusted-OR=1.57), and metals (adjusted-OR =1.40). In Table 6, children living in proximity less than or equal to 2.5 km to facilities releasing pollutants show an increased risk in childhood leukemia. Thirty seven out of seventy two pollutants showed high results. Tetrachloromethane showed an adjusted-OR of 2.23, flouranthene adjusted-OR 1.86, PAHs adjusted-OR 1.54, and arsenic/cadmium adjusted-OR 1.50. A 100% of the population exposed to benzo (a) pyrene was also exposed to benzo (b) fluoranthene, benzo (k )fluoranthene, and indeno (1,2,3-cd) pyrene. 84% of the population exposed to cadmium was exposed to arsenic as well. Also, there was some data that was not shown in either of the tables, 69% of the population exposed to nickel was exposed to arsenic and cadmium too.

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Discussions

In this study, an investigation was done to analyze the effects of being exposed to industrial and urban sites on childhood leukemia in Spain. The findings in this study supported their hypothesis that urban sites may be a risk factor in leukemia. The analysis shows an excess risk of childhood leukemia among the children living in the proximity of industrial sites. The children lived in a radius of 2.5 km. There is also an increased risk if childhood leukemia with children living near plants involved in metal sectors, glass and mineral fibers, pharmaceutical products, hazardous waste, surface treatment using organic solvents, and facilities releasing carcinogens, non HPCs, plasticizers, pesticides, solvents, POPs, PACs, metals, and VOCs. There is an inconsistency in childhood leukemia and industrial sectors which causes a concern to industrial pollution. However, there is consistency between childhood leukemia and the metal industry. There is a linkage between the installations that releases carcinogenic substances into the environment such as heavy metals, PAHs, asbestos, benzene and dioxins. An earlier study was done by Knox. In the study Knox found that, “The search showed two important heterogeneities. Firstly, certain steelworks showed powerful and probably independent effects... Secondly, despite the predominant effects of refinery and petrochemical installations, a group of large refineries seemed to be relatively innocent” (1994). Three years later another study was done by Knox and Gilman. “The associations with car manufacture and with galvanizing suggest alternative non-solvent exposures: namely to metal casting, metal forming and welding. Examination revealed short range risks associated with aluminum, zinc, and iron and steel casting” (Knox and Gilman 1997). In this study, there was an excessive risk for tetrachloroethylene and dichloromethane. The excessive risk for tetrachloroethylene and dichloromethane are shown in table 6. Back in 1990 and 1994 Fagliano and Cohn, “performed a study which have linked exposure to drinking water contaminated by tetrachloroethylene and trichloroethylene to an increase in incidence of some childhood leukemia”. This study showed specific groups of pollutants. Whereas Reynolds did a study in 2003, “found an association between increased childhood leukemia rates and high exposure scores for 25 potentially carcinogenic hazardous air pollutants (including benzene, dioxins, tetrachloroethylene, and vinyl chloride) released from mobile, area, and point sources”. Urban air pollution is a risk factor for childhood leukemia. This is a known fact because the findings in this study are consistent with other studies s (Boothe et al., 2014; Crosignani et al., 2004; Filippini et al., 2015; Vinceti et al., 2012). Surprisingly, there is an inverse relationship between the excess risks urban areas and industrial distance from OR-adjusted=1.16 for urban areas with industrial distance of 1 km to OR-adjusted=1.41 for urban areas in 5 km. According to García-Pérez there is, “A possible explanation for this could be that the increase in industrial distance entails reducing the urban and reference areas (see Fig. 1), something that allows for the establishment of a “cleaner” reference zone with increasing industrial distance (reference areas having no industry in a radius of 5 km will be “cleaner” than reference areas having no industry in a radius of 1 km, i.e., it is possible that many children included in the reference area for the example of industrial distance of 1 km are “actually exposed” to industrial pollution and, therefore, the estimated ORs for urban areas are lower than for industrial distance of 5 km)” (2015).

Strengths

One of the main strengths that I read in this article is that they had a big control group; there were almost 20 controls per case. The bigger the control the more reliable the results and it gives a more spatial distribution of the population at risk. Another strength in this study would be that they randomly selected the controls. Randomly selecting the controls is a major key in a population based control study because it reduces selection bias. “This implies the possibility of having cases included in the control group, since the exclusion in that group could bias the results (Grimes and Schulz, 2005)”.

Weakness

A weakness would be the confounding factors that are related to distance. Real exposure is dependent on the prevailing winds, geographic landforms, and released into an aquifer which limits the capacity to find positive results. Another weakness of this study could not know if the parents were exposed to industrial or urban sites while working. Trying to figure out what causes a disease you need to weigh out all options because parents play a huge role in their children’s life as well. Questions How can childhood leukemia be prevented? Is there a way to isolate industrial and urban sites from homes? Is there any way to really keep our children or even us ourselves out of harm’s way? There is no way to really prevent childhood leukemia. If industrial companies and urban sites actually planned out or bought land farther away from homes or close to town then it would actually be a start of something new or safer for people. Honestly, there is nowhere safe. Harmful things are all around us.

Conclusion

Every day is a new day and each day we will all learn something new; whether it’s to learn how to ride a bike or the risk factors of childhood leukemia. This study revealed evidence that living in the proximity of industrial and urban sites can be a risk factor for childhood leukemia. Children that lived near industrial plants and urban area showed an excess risk. An analysis also showed an increased risk in childhood leukemia to children living in the proximity of installation releasing carcinogens.